Projection of motion pictures



ame E936., w. CARPENWR @@45932@ I PROJECTION OF MOTION PICTURES FiledSept. 28, 1953 2 Sheetsfsheet l ATTORNEY A. w. CARPENTER l@ PROJECTIN OFMOTION P'ICTURES Filed sept. 2s, 1933 2 sheets-snee@ 2 BY W ATTORNEYPatented June 23, 1936 y FPATENT OFFICE 2,045.12 PROJECTION OF MOTIONPICTURES Arthur W. Carpenter, New York, N. Y., asaignorlto UnitedBescarchCorporation, Long Island City, N. Y., a corporation of DelawareApplication Scptember'Z, 1933, Serial No. 691,264

6 Claims. (Cl. 88--16.6)

The invention relates to anl improved method and apparatus forpresenting stereogram's for viewing by projection.

I have heretofore proposed to produce a stereogram on lm. However,regardless of the particular type' of interlined stereogram which may beachieved on fllm, whether it be plain parallax stereograms containing.two interlined stereoscopic images or interlined stereograms of thepanoramagramic type as described by others orstereograms containinginterlined groups of duits object azimuth or station views, as describedin my applications Serial Nos. 69,829 and 690,830,

blocked out or Wasted by theanalyzing screen.

lf, as is the case in most instances, the ratio oi' transparentspaces toopaque lines in the said analyzers is as one clear unit to severalopaque units, for example, one tofour or one to nine, then it is obviousthat an even larger proportion of the available light is Wasted by theanalyser. In the last mentioned case, this wastage mns as high as 90% ofthe available light.

Even when other types of analyzers, such as ribbed transparentrefracting screens are used, the economy of available light is only alittle higher, and this waste of light is an inherent feature of thepresentation for viewing of pm'- allax stereograms.

An object of the present invention is to oliset this waste of light, andto increase thescreen illumination of the projected ster.

The method and means which I here describe donot propose to alter thisinherent quality oi!l light wastage in the interlined stereograms, butdo propose to offset this discrepancy to -a large extent by" increasingthe light emciency of-the 'apparatus by which the stereogram ispresentedv for viewing. I do not seek to accomplish this cnd byincreasing the brilliancy ot the light sources, because such sources ofblinding intensity Another object of the invention is to present theprojected stereogram for viewing by a large number of people such as atheatrical audience.

Another object of the invention is to obviate the necessity, inprojecting a large stereogram image, of accurate registration betweenthe picture line elements of the stereogram with the lines of the linescreen.

The preceding object is accomplished by em-f bodying a ribbedtransparent refracting screen on the film which carries stereogramsrepresenting the successive kinematic phases of the action, and byprojecting the lineated stereograrns therev in as real aerial images.The projection of real `aerial images avoids thenecessity 'for aphysijf, projection screen.

The use of aerial images therefore eects an economy of light and avoidsa physical screen. Both of these features while particularly applicableto the projection ci motion pictures in stereoscopic relief, aregenerally useful in still or motion pictures, whether ordinary black andWhite pictures, or pictures in color with or without stereoscopicrelief.

The embodiments which Si propose may be better understood if l firstdwell briefly upon several of the concepts which underlie the methodsand apparatus which I propose to use.

in the case of the simple projection oi' an image on to a reectingscreen by means of the customary type or projection apparatus, it willbe seen that only a portion of the sphere of light emanating from thelight source is collected by the lens of a condenser system and by thiscondenser directed toward the objective through the hlm or transparencywhich it is desired to proiect. l

A spherical angle or cone of initial radiation which is collected by theproximal lens of the condenser represents the greatest amount of lightenergy available for the projection. This available energy is reasonablyconserved during its passage through the condenser and its convergenceto the projection objective, but at this projection objective and fromthis point on, large quantities of the available light are sodistributed and dispersed as not to be available to the observer forwhose use the light is presumably projected.

In order that the projected image appear to be more or less evenlyilluminated, it is necessary that the reflecting surface be a surfaceyielding highly diffused reflection. In other words, every point of thisreilecting surface shall reect almost equally in all directions thelight which is incident upon .it from any direction. From this itfollows that the light directed toward the eye of the observer from anypoint of the refiected image v can be at best but a minute part ofthevlight which entered into the formation of that image at that point, andhence the apparent brilliancy of the reflected image can be at best buta minute part of the actual brilliance of the image.

Now, itis often proposed in projection practice that this reectingsurface should be made specular rather than diffuse in its nature. Ifthis is done to its fullest extent, and a plain specular reflectingsurface, such as a mirror, substituted for the diffused refiectingsurface of the ordinary screen, it is found that a much lesssatisfactory -result is achieved.

In this case, by the laws of incidence and reection, most of the lightwhich enters into they formation of the image at the screen, is sodlrected by reection that no part of it can reach the eye of theobserver, land hence the portions ofl small portion of the reector'within which. the

projection objectivecan by the laws of incidence and reflection directlight into the observers eye, is useful for viewing an image by specularredection. Within this tiny area, howsoever, the illumination of theimage by the ordinary types of illuminants and projection optics isdazzlingly intense, and in order to make it possible to view the imagein such an apparatus, it is necessary to reduce the intensity of theilluminant from that of the usual projection lamp, for example, to thatof a low wattage frosted or ashed lamp bulb.

Insofar as this specular type of reiiection can be used, then it is seenthat there is in eiect an enormous economyof available illumination,and,

it is this principle which I employ for the more eiilcient projection ofparallax stereopanoramagrams and 'the like.

Pausing yet a moment to considerv further inherent differences betweenspecular and diffuse reiiector, it is seen that in the case of a diiuserefiector, if the image formed by the projection apparatus is formedelsewhere than at the surface'of the diffused reflector, only a blurredor indistinct image c an be seen by the observer. In the case of aspecular` reflector, this limitation does not apply, and insofar as theimage can be seen by the observer, it maybe formed at the surface ogthereflector or before or beyond the surface o the reflector equally well,the only difference so faras the observer is concerned being in theapparent size and position of the image which is formed.

Now, if a specular reflector can be used which makes it possible for thevirtual image ofthe projection objective to subtend the angle of view ofthe 'observers eye when the latter is directed toward any part of theprojected image, then the aforementioned enormous economy ofillumination will prevail throughout the area of the projected image. i

Such a condition is obtained by this invention by the use of a specularreflector having a conacechan set-up, or to-fulll certain specialrequirements it may be parabolic, hyperbolic, or ellipsodal in With eachof these forms, conditions may be established such that as the observerlooks to- 5 wards any part of the projected image, he will see thatpoint of the image against the background of the radiant light source,and it will therefore appear to be brilliantly illuminatedeven when thelight source is of very low intrinsic intensity. Vl0

With the conic forms of concave surfaces, these conditions may befulfilled for limited viewing positions with very great efficiency. Withthe spherical forms of concave surfaces, these conditions can befulfilled reasonably well 15 for a large number of observers with acomparatively high'degree of efficiency, and `by the use of such areflecting surface, much of the disadvantage inherent to the wastage oflight in showing aparallax stereogram may be offset because the 20 gainin light by the eflicient use of specular reiiection is often greaterthan the loss of light due to analysis of the parallax stereogram.

In practice, I generally make use of the plain spherical or slightlyparabolized concave reflector 35 y of .comparatively long radius ofcurvature, it being only necessary that the area of said reflector begreat enough to fulfill the aforementioned requirements throughout asgreat a held of view as is to be 'utilized by the observer or observers.3U Of course, in theatre projection, this means that nearly the wholebackground of the ordinary stage area must be covered by the concavereector, and this means a pretty large reflector of this nature, butthere are certain ameliorating circumstances which makes such anapparatus more practical than it might at first seem, and I shallmention these circumstances presently. meanwhile, I wish to refer againto the fact that with a specular reflecting surface, the image li0formed by the projector may be positioned elsewhere than at the surfaceof the reflector, and.' this property I make use of in my apparatus togain an added `convenience in projection by this method and tofacilitate the showing of a com- 45 paratively large image with acomparatively short projection throw.

For further details ofthe invention reference may be made to thedrawings wherein Figure 1 is a, schematic side elevation of pro- 50jection apparatus, particularly applicable to ordinary motion pictureprojection according to the present invention, the projector being'located above the audience as in standard theatre practice.

Figure 2 is a schematic side elevation of an alternative, wherein theprojector is arranged close to and below the center of the reectingmirror, resulting in a magnified image, useful with ordinary nlm or withthe nlm of Figure 5 60 for stereoscopic relief.

Figure 3 is a schematic side elevation of a modification of Figure 1employing a real screen out of the direct line yoi view of the audience,with means for forming an aerial image of the 65 ordinary still ormotion picture projected on the real screen.

Figure 4 ls a further 4alternative wherein a ribbed lenticular reflectorconcealed from the audience is employed for analyzing a stereogram whichis projected for viewing, as a real aerial image.

Figure 5 is an'enlarged sectional view of motion picture film foruse/with Figure 2 and having an interlined kinematic stereogram thereonand integral with a lineater comprising cylindrical ribs.

projector Iv is arranged to abaxially project the pictures on ordinaryfilm onto the spherical reector 3 having a center of curvature at 29. By

` abaxiallyprojecting the picture onto reector 3,

, I focuses the images on film 23 in the plane 9,

which is distant from the reflector 3 in amount equal to the radius ofcurvature R of the reflector 3. A'Ihere is no screen provided in theDiane 9 and the focused image there formed is unobservable by theaudience in seats such as I0 in the theatre. In this case the aerialimage 3 is formed on the stage II at ardistance from the reflector 3equal tothe radius of curvature R thereof. The projector I may befocused to bring the image plane 9 closer to the reflector 3 than abovedescribed, whereby the aerial image 8 will vbe larger than the image inplane 9, or the projector I may be focused to bring the image plane 9farther away from the reflector 3 than is illustrated in Figure 1whereby tlie aerial image 8 will be smaller than the image in plane 9.In fact the locus of plane 9 may substantially coincide with.

thesurface of reflector 3.

As illustrated, a segment of a spherical reflector may be employed withthe bottom edge of this reflector substantially parallel with the floorof stage II. The horizontal width of the bottom of the reflector 3 at ornear the floor of the stage, ad in a direction at right angles to thedrawings, is comparable to the width of the first horizontal row ofobserving stations or theatre seats I2.

The arrangement in Figure 1 conforms to standard theatre practice as theprojector I is arranged above the audience, .with a long projectionthrow from the projector I to the reflector 3.

Figure 2 illustrates an alternative wherein the projector. I 5 isabaxially arranged below the center line of the spherical reflector 3,and also arranged closer to the reflector 3. The center of curvature ofreflector 3 is illustrated atv30. In

this case the projector I5 is provided with a wide.

angle projection objective I6 to fill the front surface of thereflector3 with light. In Figure 2 the real aerial image is formed in "the planeI1 on the stage II, without the use of a screen as "before, theprojector I5 being located below the integral therewith cylindricalribbing I4 which extends lengthwise of the fllm and which serves as aline'ate; for the stereogram record I3.

'I'he stereogram film record 2, a sectional view which isillustrated inFigure 45, may be prepared .Referring in detail to the drawings,picturein any one of a number of dierent ways as above described. In anycase, the successive frames of Afilm 2 contain records of successivekinematic phases of a moving object, each such phase being recorded asan interlined stereogram, wherein a stereoscopic record appears as aninterlineation of picture elements.

For recording an interlined stereogram on fllm, I find it satisfactoryto use more than 300 and less than 600 lines per inch. For example, 35mm. lm has about 420 lines or ribs per inch,

thereV being a corresponding number, lthat is, 420

groups of picture elements I3 in each frame of the film.

In Figure 3 use is made of a real'screen I9 which is below the stage II, however, and therefore out of the direct line of 4view of theaudicnce.l The projector 23 which is similar to the projector in Figures1 and 2, the lm gate of which need not necessarily be tilted however,pro

jects anordinary still or motion picture from vfilm l l 28 onto thescreen I9 which is abaxially arranged with respect to the center line ofreflector 3, a

real aerial image of the ordinary still or motion picture being formedin the plane 2| on the stage' II. lThe center of curvature of reflector3 as shown in Figure 3 is between the bottom of aerial image 2l and thetop of screen I9.

Figure 4 illustrates a further alternative wherethe projector 2i by a.ribbed reflecting analyzer 23 which is abaxially arranged with respectto the center line of reflector 3 to form a real aerial kinematicstereoscopic image in the plane 24 on the stage II. 'The line pitch ofthe stereogram on fllm 22 is projected in register with the ribs onanalyzer 23. l

The formation of real aerial images by the concave spherical reflector 3is subject to well known and fully described optical laws, and admits ofmagnification or miniflcation according to laws very similar to thosewhich govern the formation of images by refractinglenses. 'I'hesereflector images, however, are free from defects v due to chromaticaberrations, and in respect to certain other aberrations common torefracting lenses, they are superior to refracted images.

Moreover, within reason, it is more convenient to form abaxial imageswith a concave reflector by abaxial displacement of the object than itis to correspondingly form abaxial images with a refracting lens. Thisfact I also make use of Ain the apparatus of Figures 1-4, in that it isconvenient in setting up such apparatus for theatre projection to makeuse of abaxial projection to a sufllcient extent to just convenientlyavoid physical interference between the line of projection and the lineof observation.

Now, if we consider an aerial projected image as seen by'the observer,it will become evident that the only portions oi the concave reflectorwhich enter into the formation of that image so far as that observer isconcerned, is that portion-of the reflector subtended bythe image. Inotherlwords, the only useful portion of the reflector is that portionembraced by the boundaries of the image, if the said boundaries arevprojected back against the reflector from'a point located at the eye ofthe observer. This in practice is foundto, be a portion of theTreflecting Surface only somewhat greater than the actual area of theimage, and if more than one observer is to be simultaneously served bythe reector, it is found that only that portion of the reflector whichis necessary to subtend a spherical angle great enough to include all ofthe desired vviewing positions is required.

In practice I find that little more than the upper half of the sphericalreflector having av horizontal chord approximately equal to the lengthof the nearest row of observing 'stations is required for satisfactorytheatre projection.

In most instances, it is not necessary to use the uppermost portions'ofeven this half since the upper part of thereector would only beserviceable for viewing the image from a position in the orchestra pitahead of the front seats. A part of my invention therefore consists inthe use of a selected portion of a concave reflecting surface for theformation of the image which is to be viewed by the audience. Nor do Iparticularly limit myself to any particular shaped section of suchreflectors, since in the case of .one auditorium a complete zone is bestadapted, whereas for other auditoriums rectangular sections of variousproportions may serve to better advantage. 7

`Neither am I limited to any particular radius of curvature for thesereflectors, since this is a feature of the reflector which is variableaccording to the circumstances of the desired position of the image, orthe reector itself, or of the audience, andy of the sizeor position ofthe film and projecting apparatus which it is desired to use.

As a measure of convenience in the practical erection of suchreflectors, I might mention that if the reflector is spherical then itmay be convenientlyvbuilt up of a large number of individual portionssince all portions of the spherical surface embraced withinsimilaboundaries are ob- -viously identical. As to how such reflectorsmay be formed, there is embraced withiri'my' invention obviously a widescope of available practices.

I may build the reecting surface out of suitable building blocks, eachof which is a repeating unit'of such surface and specularly reect'- ingon its face, or I may use such blocksk which are not reflecting, andwhen the whole surface iserected, coat it with a suitable specularreflecting medium, as for example, by spraying it with volatilized metalto create a continuous metallic reflecting coating as by well knowncommercial metal spraying processes, or I may form this surface inplastic materials bythe use of sweeps, and surface it by spraying or`painting with substances having a high percentage of specularreflection, or yet again I may form matrix surfaces and producereflectors from them by electro-plating or other similar process.

I claim:

1. Picture projection apparatus comprising tlg combination of a concavereflector facing a number of viewing stations and comparable in width tothe horizontal Yextent of the proximate viewing stations, means. forabaxially projecting an interlined stereogram towards said reector, saidvprojector comprising means for focusing the projected stereogramat alocus in front of said reflector, whereby a' real aerial -iniage of saidstereogram is formed abaxially of said reflector Aout of the line Aofsaid projection, and means intermediate said projector and saidreflector for analyzing said stereogram to produce said real image inrelief. f A

2. Picture projection apparatus comprising the combination of a concavereflector facing a number of viewing stations and comparable in width tothe horizontal extent of the proximate viewing stations, means forabaxially projecting a kinematic interlined stereogram towards saidreflector. said projector comprising means for focusing the projectedpicture at a locus in front of said reflector, whereby a real aerialimage of said picture is formed abaxially of said reflector out of theline of said projection, and means in registry with the lineations ofsaid stereogram for producing said picture in relief.

3. In a system for projecting real aerial images for observation byobservers, said images being positioned perpendicularly to a stageplatform in front of said observers,.the combination of a projectorhaving a projection lens therein, a concave reflecting surface toreceive the light from said projector and to reflect said light to forma real image between said reflector and the observers, and means withinsaid projector for abaxially positioning the iilm'to produce the imagebeing reflected at a predetermined angle with respect to the viewingpoint of said observers.

4. A system for the formation of large real aerial images in relief tobe viewed by observers comprising an integral stereogram and a lineatertherefor, a projector for said stereogram said projector including amagnifying lens anterior of said stereogram, and a concave reflectingmirror so arranged with respect to the position of said sterogram insaid projector that an enlarged real stereoscopic aerial image of saidlineated stereogram is formed intermediate said reflector and theobservers, the stereogram image being enlarged in proportion to themagnifying power' images in relief at a position corresponding tol theusual location of a projection screen in a theatre, the combination of aconcave spherical reflector in the Aline of sight of an observer, aprojector out of the direct lineof sight of said observer, an interlinedstereogram in said projector, a vlineater in optical registry therewith,and a magnifying' lens in said projector, said prof :lector being soarranged and the reflector being so positioned that the said lens of theprojector and said reflector cooperate to produce an enlarged real imageof the interlined stereogram, said real image being produced at theusual location of a projection screen. i

6. In a system for observing large real aerial images at a positioncorresponding to the usual location of a projection screen in a theatre,the combination of a concave spherical reflector in the line of sight ofan assembly of observers, a diffusing screen abaxially of said reflectorand out of the line of sight of the assembly of ob-

